MidAmerican Energy Co. is ending coal ash disposal at three of its power plants and will dig up coal ash material located below the water table.

MidAmerican, based in Des Moines, said Thursday it would close coal ash landfills or ponds this year at Neal South Energy Centers near Sioux City, and at Walter Scott Jr. Energy Center in Council Bluffs this year.

Alliant Energy, the parent of Interstate Power & Light, also said it is closing coal ash ponds and landfills at the ML Kapp Generating Station near Clinton, and at generating plants in Burlington, Lansing, Ottumwa, Cedar Rapids' Prairie Creek and Sutherland, near Marshalltown.

Among the work: Alliant said it closed a 32-acre inactive pond landfill at ML Kapp in January while work to close ponds at the Burlington generating station won't begin until after that facility switches to natural gas in 2021.

Federal regulators say the coal ash ponds can contain contaminants such as mercury, cadmium and arsenic and pose a threat to public health if not properly disposed of.

Both Alliant and MidAmerican said some results require additional testing, but added that none of the ponds pose a public health risk.

MidAmerican said it stopped sending coal ash to a Louisa Generating Station pond in Muscatine last year and began work to close it.

The Berkshire Hathaway-owned utility said it would dig up coal ash material located below the water table as it closes ponds at Neal North and Walter Scott plants.

MidAmerican said it would recycle as much of the coal ash as possible or dispose of it in lined landfills no later than August.

Alliant said it plans to close all its coal ash ponds by the end of 2023.

With its remaining coal plants, the utility said it will move to a system that doesn't require water to move coal ash, so ponds will no longer be needed.

Register reporter Donnelle Eller and the Associated Press contributed to this report.